Project description:Background: The presence of abundant tumor stroma is a prominent characteristic of pancreatic ductal adenocarcinomas (PDAC) that potentially influences disease progression and therapy response. This study aims to investigate immune cell infiltration and epigenetic profiles in tumor cell enriched (“Tumor”) and stroma cell enriched (“Stroma”) regions within human PDAC tissue samples to identify regional-specific genetic alterations as a basis for novel drug target development. Methods: Formalin-fixed paraffin-embedded (FFPE) tumor tissue samples were obtained initially from 15 patients who underwent PDAC resection. Tumor and Stroma regions were separately assessed for their immune cell composition by using immunohistochemistry (IHC) and epigenetic modifications based on DNA methylation obtained by Infinium MethylationEPIC microarrays. A tissue microarray cohort of additional 65 PDAC patients was included for validation of IHC findings and survival analysis. Results: By comparing Tumor and Stroma defined regions of PDAC tumors, we identified 25,410 differentially methylated positions (DMPs) distributed across 6,963 unique genes. Pathway enrichment analysis using the top 2,000 DMPs that were either hyper- or hypomethylated, indicated that immune response pathways and the estrogen receptor pathway are epigenetically dysregulated in Tumor and Stroma regions, respectively. In terms of immune cell infiltration, we observed overall low levels of T cells in both regions. In Tumor regions however, occurrence of tumor-associated macrophages (TAMs) was higher than in Stroma regions (p=0.02) concomitant with a dualistic distribution that stratifies PDAC patients into those with high and low TAM infiltration. By categorizing TAM levels into quartiles, our analysis revealed that PDAC patients with more than 1,515 TAMs per mm², representing the upper quartile, exhibited significantly shorter overall survival (p=0.036). Conclusions: Our data suggest that variations in inflammatory characteristics between the Tumor and Stroma defined compartments of PDAC may primarily stem from the presence of macrophages rather than lymphocytes. The abundance of TAMs within regions enriched with tumor cells correlates with patient survival, underscoring the potential significance of exploring therapeutic interventions targeting TAMs. Furthermore, directing attention towards the estrogen receptor pathway represents a promising strategy to address the stroma cell component within the PDAC tumor microenvironment.

Project description:Immunotherapeutics represent highly promising agents with the potential to improve patient outcomes in a variety of cancer types. Unfortunately, single-agent immunotherapy has achieved limited clinical benefit to date in patients suffering from pancreatic ductal adenocarcinoma (PDAC). This may be due to the presence of a uniquely immunosuppressive tumor microenvironment (TME) present in PDACs, which creates a barrier to effective immune surveillance. Critical obstacles to immunotherapy in PDAC tumors include the dense desmoplastic stroma that acts as a barrier to T-cell infiltration and the high numbers of tumor-associated immunosuppressive cells. We have identified hyperactivated focal adhesion kinase (FAK) activity in neoplastic PDAC cells as a significant regulator of the fibrotic and immunosuppressive TME. We found that FAK activity was elevated in human PDAC tissues and correlates with high levels of fibrosis and poor CD8+ cytotoxic T-cell infiltration. Single-agent FAK inhibition (VS-4718) dramatically limited tumor progression, resulting in a doubling of survival in the p48-Cre/LSL-KrasG12D/p53Flox/+ (KPC) mouse model of human PDAC. This alteration in tumor progression was associated with dramatically reduced tumor fibrosis, decreased numbers of tumor-infiltrating immature myeloid cells and immunosuppressive macrophages. We postulated that these desirable effects of FAK inhibition on the TME might render PDAC tumors more sensitive to immunotherapy. Accordingly, we found that VS-4718 rendered the previously unresponsive KPC mouse model responsive to anti-PD1 and anti-CTLA4 antagonists leading to a nearly tripling of survival times. These data suggest that FAK inhibition increases immune surveillance by overcoming the fibrotic and immunosuppressive PDAC TME thus rendering tumors more responsive to immunotherapy. We treated KP orthotopic tumor-bearing mice with vehicle and FAK inhibitor (FAKi) for 14 days, then extracted total RNA from tumor tissues.

Project description:Pancreatic ductal adenocarcinoma (PDAC) displays a poor response to immunotherapy. This poor response is predominantly attributed to the highly immunosuppressive tumor microenvironment (TME), characterized by a scarcity and dysfunction of infiltrating CD8+ T cells. Epigenetic regulators have recently been implicated in immune escape and immunotherapy sensitivity, presenting an appealing approach for directly targeting epigenetic factors or combining epigenetic therapies with immunotherapy in PDAC. Our study is the first to delineate the regulatory function of the epigenetic factor Sin3B in the tumor immune microenvironment (TIME) of PDAC. Using murine PDAC models, we discovered that intrinsic Sin3B loss in tumor cells reshapes the TIME, manifested by increased CD8+ T cell infiltration into tumors through enhanced secretion of CXCL9 and CXCL10. This was accompanied by an increase in the cytotoxicity of CD8+ T cells, as evidenced by elevated Granzyme B (GzmB) and IFNγ production. Furthermore, Sin3B-deficient tumor cells exhibited heightened secretion of CXCL9/10 in response to IFNγ, creating a positive feedback loop via the CXCL9/10-CXCR3 axis and thus intensifying immune response against PDAC. Additionally, loss of Sin3B increased PDAC susceptibility to anti-PD1 therapy in mice. Corroborating our findings in the mouse model, analysis of human PDAC samples demonstrated a significant inverse correlation between Sin3B levels and both CD8+ T cell presence and CXCL9/10 expression. Notably, PDAC patients with lower Sin3B expression exhibited a more favorable response to anti-PD1 therapy. Concerning the mechanism, we systematically uncovered the extensive epigenetic regulation employed by Sin3B loss via the modulation of H3K27Ac redistribution in PDAC cells. Sin3B deficiency resulted in an uptick of H3K27Ac peaks concentrated in the promoter and enhancer regions. Under the treatment of IFNγ, Sin3B loss leads to the enrichment of H3K27Ac peaks in promoter regions of ISG-related genes such as CXCL9 and CXCL10, thereby boosting their expression. Collectively, our research outcomes propose a potential target for enhancing the accessibility of cytotoxic T cells to the tumor site and improving immunotherapy in the challenging landscape of PDAC.

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Identification of cold tumor induction–related markers in pancreatic cancer and the clinical implication of PCDH7

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